1. Field of the Invention
This patent relates to liquid dispensing cartridges for automated dispensing systems. More specifically, this patent relates to a dispensing valve system attachable to an ink cartridge that automatically opens and closes in response to pressure from the ink.
2. Description of the Related Art
Lithography is a printmaking process dating back to the 1700s in which ink is applied to a plate having both image and non-image areas. The image areas are ink-receptive and water-repellent. The non-image areas are water-receptive and ink-repellent. In rotary type lithographic presses the ink plate is mounted on a cylinder that rotates during printing. In one typical configuration, the plate cylinder picks up the ink at the image areas and transfers the image to a blanket cylinder which then transfers the image to the paper.
In multi-color sheet-fed presses, up to ten inking stations can be placed in series. Each station has its own ink feeding system and handles a separate color. As the paper sheet moves from station to station, a new color is put down at each station.
Because lithographic ink is thixotropic, conventional lithographic ink feeding systems require a complex system of drums, vibrators and fountain rollers. In a typical lithographic ink feeding system, workers remove lithographic ink from a drum (or, in some cases, smaller tins) with specially made spatulas and spread the ink across a tray (the ink fountain). Fountain rollers roll against the ink fountain to pick up the ink and transfer it to the plate cylinder. The process is labor intensive and subject to error.
Storing lithographic ink in drums can result in wasted ink if the entire drum is not used because it is difficult to store and reuse ink in drums. The lithographic ink itself is prone to oxidation which can result in color variations from one press run to another, and even from sheet to sheet within a single run. In addition, upon exposure of the ink to the atmosphere, volatile organic compounds (VOCs) evaporate, which can cause ink spoilage.
Consequently, many modern printers, including sheet fed lithographic printers, use smaller cartridges to dispense ink. During printing the ink cartridge moves back and forth across the fountain, dispensing ink into the fountain or directly onto an ink form roller to provide an even, consistent layer of ink. In automated presses, the amount of ink in the fountain is continually monitored and replenished as needed.
Ink cartridges can be easily filled, transported, used and reused. The cartridge minimizes exposure of the ink to the atmosphere and also minimizes the amount of residual ink left in the cartridge after use. The cartridge typically comprises a hollow cylindrical body, a plunger at one end and a dispensing fitment at the opposite end. The cylindrical body is filled with ink. The plunger serves as a piston within the cylindrical body to extrude the contents of the dispenser when the plunger is forced toward the dispensing end by, for example, pneumatic pressure.
The dispensing fitment is mounted in sealing engagement within the dispensing end of the cylindrical body and has a valve and nozzle for controlling the flow of ink. In one ink cartridge described in U.S. application Ser. No. 09/470,747, now U.S. Pat. No. 6,192,797 owned by the assignee of the present application, the valve is recessed below the edge of the cartridge and the nozzle extension is detachable so that the valve and nozzle extension do not become damaged during shipment. When ready to use at the printing plant, the nozzle extension is attached to the recessed valve and extends beyond the end of the cylindrical body. The valve must be manually opened to allow ink to flow.
While this type of dispensing cartridge is suitable for its particular purpose, it requires that the valve be manually opened and closed. Thus there exists a need for an improved ink cartridge dispensing valve system that operates in response to pressure from the ink to open and close.
Therefore it is an object of the present invention to provide an ink cartridge dispensing valve system that opens and closes in response to pressure from the ink.
Another object of the present invention is to provide an ink cartridge dispensing valve system that can be attached to a recessed universal attachment post at the printing press.
A further object of the present invention is to provide an attachable dispensing valve that can be used in a sheet fed lithographic printing press with a hand gun or with an automated printing system.
Still another object of the present invention is to provide an ink cartridge dispensing valve system that minimizes exposure of the ink to the atmosphere.
Yet another object of the present invention is to provide an ink cartridge dispensing valve system having a recessed universal attachment post for easy packing, shipping and storing.
Further and additional objects will appear from the description, accompanying drawings, and appended claims.
The present invention is an improved ink cartridge of the type used to dispense ink in automatic lithographic presses. The ink cartridge comprises a hollow cylindrical body for holding a supply of extrudable ink and has a dispensing end and a plunger end. The plunger end is closed by a plunger adapted to serve as a piston within the cylindrical body to extrude the contents of the dispenser when the plunger is forced toward the dispensing end by pneumatic or mechanical pressure. The dispensing end is closed by a dispensing fitment affixed thereto by glue or other suitable means. The improvement comprises an attachment post mounted over a central aperture in the dispensing fitment, the attachment post having a sidewall and a top wall, the top wall having a plurality of openings therein; a nozzle mounted over the attachment post and defining a substantially cylindrical space; a plate mounted within the substantially cylindrical space, the plate having a central opening; and a spring mounted within the substantially cylindrical space on the side of the plate away from the attachment post top wall to bias the plate in sealing engagement with the attachment post top wall. When pressure is exerted on the plate by the ink, the spring compresses, allowing ink to be extruded through the nozzle.